1. Saute onion, celery, leek and garlic until wilted, about 5 minutes.
2. Stir in flour until smooth; cook over low heat, stirring constantly, 3 minutes.
3. Whisk in 5-1/2 cups broth; simmer until vegetables are very soft, about 15 minutes.
4. Meanwhile, puree avocado with 1/2 cup broth in a food processor or blender.
5. When vegetables are done, stir in avocado; simmer 10 minutes.
6. Stir in lime juice, cilantro, and salt and pepper to taste.
7. Divide soup among 6 warmed soup bowls.
8. Garnish each with a dollop of creme fraiche and a few strips of pimiento.

*Large avocados are recommended for this recipe. A large avocado averages about 8 ounces. If using smaller or larger size avocados adjust the quantity accordingly.